FIG. 1 is a diagram showing the structure of a prior art image display system.
In the figure, reference numeral 1 denotes a light emitting body, reference numeral 2 denotes a parabolic mirror for reflecting light emitted out of the light emitting body 1 so that the light becomes substantially parallel light, and reference numeral 3 denotes a converging lens for converging the light reflected by the parabolic mirror 2. An illuminating light source system is comprised of the light emitting body 1, the parabolic mirror 2, and the converging lens 3.
Reference numeral 4 denotes a light valve for spatially modulating the intensity of the light converged by the converging lens 3 based on image information, reference numeral 5 denotes a projecting optical lens for projecting the light whose intensity is modulated by the light valve 4, and reference numeral 6 denotes a screen for displaying, as an image, the light projected thereonto by the projecting optical lens 5. Optical paths are designated by arrows in the figure.
Next, a description will be made as to an operation of the prior art image display system.
Light emitted out of the light emitting body 1 is reflected by the parabolic mirror 2, and is then converged to the light valve 4 by the converging lens 3. The light valve 4 spatially modulates the intensity of the light converged by the converging lens 3 based on image information. The light whose intensity is modulated by the light valve 4 is projected onto the rear (i.e., a left-side surface as shown in FIG. 1) of the screen 6 by the projecting optical lens 5, and is displayed as an image on the screen 6. A user of the image display system can check the image visually from a front surface of the screen 6 of FIG. 1 (i.e., a right-side surface as shown in FIG. 1).
The image display system of FIG. 1 has a depth corresponding to a distance between the illuminating light source system comprised of the light emitting body 1, the parabolic mirror 2, and the converging lens 3 and the screen 6. It is preferable that such an image display system that can display an image of an identical size is so constructed that the depth thereof is provided as thinly as possible. For this reason, the prior art image display system as shown in FIG. 1 displays an image on the screen 6 by using a wide angle projecting optical lens 5 so that the depth of the image display system can be reduced and therefore the image display system can be slimmed down.
However, because the prior art image display system of FIG. 1 has a limitation on how wide angle the projecting optical lens 5 has, in order to further slim down the image display system, the prior art image display system further includes a plane mirror 7 that is inclined at 45 degrees with respect to a horizontal direction, for bending the optical path extending from the projecting optical lens 5, and for projecting the light from the projecting optical lens 5 onto the rear of the screen 6, as shown in FIG. 2.
In the image display system of FIG. 2, some components, such as the illuminating light source system, the light valve 4, and the projecting optical lens 5, are arranged in a direction of the height of the image display system (i.e., in a vertical direction of FIG. 2), and the slimming down of the image display system can be further implemented. In this case, the depth of the image display system corresponds to the distance between the plane mirror 7 and the screen 6. Although the image display system can be further slimmed down by enlarging the inclination angle of the plane mirror 7 with respect to the horizontal direction to more than 45 degrees, the light valve 4 and the light source unit interfere with the projected light, and therefore the light is eclipsed and then deviates from the optical path to the screen 6.
Japanese patent application publication (TOKKAIHEI) No. 6-11767 discloses an image display system for reflecting light by using a convex mirror, instead of the plane mirror 7 as shown in FIG. 2, and for enlarging and displaying an image on a screen 6. However, this prior art image display system suffers from a drawback of displaying a distorted image on the screen 6.
A problem with prior art image display systems constructed as mentioned above is that there is a limitation on the slimming down of the prior art image display system, and the prior art image display system cannot be further slimmed down.
The present invention is proposed to solve the above-mentioned problem, and it is therefore an object of the present invention to provide an image display system that can enlarge and display an image while reducing distortion of the image and that can be further slimmed down as compared with prior art image display systems.